1. Field of the Invention
The present invention relates to an optical isolator having a structure which allows accurate and easy assembling.
2. Description of the Background Art
The conventional optical isolator as shown in FIG. 10, for instance, provides respective birefringent crystal plates, 1A, 3A, 1B and 3B,each on both sides of Faraday rotators, 2A and 2B, and magnets 20 are provided on Faraday rotators' circumference [Japanese Patent Laying-Open No. 6-242403 (1994)]. Lenses 21A and 21B, and optical fibers, 22A and 22B, are provided on the both sides of the optical isolator.
When one Faraday rotator is provided, the isolation of the optical isolator is at the highest, about 40 dB . On the other hand, when a plurality of Faraday rotators are provided, the isolation of the optical isolator is further improved (The Electronic Information Transmission Society: Proceeding 90/5 Vol. J73-C-1 No. 5).
In order to manufacture an optical isolator having a plurality of Faraday rotators, assembly must be accurately made of many optical elements and must be small. Further, a plurality of magnets must be assembled into optical isolator accurately and easily. Reciprocation action between magnets makes changeful the position of magnets. It makes more difficult the adjustment of magnets and Faraday rotators and the fixation a main body's optical isolator on a housing body.